Abstract

The field distribution inside a random waveguide has been measured over a spectral range in which the wave is nominally localized. In addition to spatially and spectrally isolated modes, extended field distributions known as necklace states are found inside random samples due to the spectral overlap. Necklace states are shown to be a superposition of multipeaked quasimodes. We performed numerical simulations that demonstrate the robustness of these spectra to variations in the random structure. We also used simulations to investigate the impact of dissipation on transmission and reflection spectra and upon the field distribution of quasimodes.

Figures (6)

(a) Spectra of the field amplitude at each point along a random sample normalized to the amplitude of the incident field. (b) Log of the field magnitude along the sample for an evanescent wave (dotted curve) and two localized modes.

(a) Spectra of the field amplitude at each point along a random sample with spectrally overlapping peaks normalized to the amplitude of the incident field. (b) Log of the field magnitude along the sample for an evanescent wave (dotted curve) and a multipeak quasimode. (c) Top view of (a) in logarithmic presentation.